Various light sources may be used for wavelength-division-multiplexing in optical transmission equipment to generate light of a desired wavelength. Some light sources may not stably generate light of a desired wavelength, and may not have a narrow line width for reduced color dispersion. In addition, these light sources may not have a large side mode suppression ratio for reduced crosstalk with adjacent channels. Thus, the light sources may not be optimal for use in a wavelength-division-multiplexing optical network. Some light sources, such as a narrow band distributed feedback laser, may not be economical for mass distribution in an optical communication system.